1. Field of Invention
The present invention relates to magnesium alloys excellent in fluidity and suited for various high pressure casting processes such as a metal injection molding, a die casting or a squeeze casting, and to materials of said magnesium alloys produced by injection of half molten metal.
2. Related Technolgy
Because magnesium alloy has a characteristic of light in weight and high in strength, a magnesium alloy has been used to such as cases of electronic portable devices, and gradually widened application ranges and amounts. For making these members hitherto, there have broadly been employed various high pressure casting processes such as metal injection moldings, die castings or squeeze castings.
As magnesium alloys available to the high pressure casting, the following Mgxe2x80x94Al based alloys have been standardized. Numerical values shown under are mass % as a unit.
(1) Multi-purposed alloy 9Al-0.6 Zn-0.3 Mn-Rest Mg (AZ91D)
(2) High ductile alloy 6Al-0.3 Mn-Rest Mg (AM60B)
(3) High ductile alloy 5Al-0.3 Mn-Rest Mg (AM50A)
(4) High ductile alloy 2Al-0.3 Mn-Rest Mg (AM20)
(5) Heat resistant alloy 4Al-1 Si-0.4 Mn-Rest Mg (AS41B)
(6) Heat resistant alloy 2Al-1 Si-0.2Zn-0.4 Mn-Rest Mg (AS21)
(7) Heat resistant alloy 4Al-2 Mm-0.3Mn-Rest Mg (AE42)
These magnesium alloys are regarded to have relatively high strength, exhibit good flow of molten metal also in the casting process. For example, AZ91D alloy as the multi-purposed alloy is good not only in the fluidity but also in the strength and corrosion resistance, and it has been used, as a balanced alloy, to major parts (about 90%) of products of magnesium alloys.
Recently, electronic portable devices have been demanded to have lighter weight, and casings of thickness being 1 mm or smaller and lighter weight are required. However, in the prior magnesium alloy (such as AZ91D) having the relatively good fluidity, in case products of small thickness as 1 mm or lower are about to be made through the high pressure casting process, there occur problems of easily causing defects in surface owing to bad flow of a molten metal, decreasing a yield of production.
The invention has been realized against a background of the above circumstances, and it is an object of the invention to provide magnesium alloys having a more improved fluidity in comparison with prior materials and applicable to production of products of thinner thickness, and to provide materials of magnesium alloys produced by the injection molding process using the above mentioned alloys.
For solving the above mentioned problems, among the inventive magnesium alloys, a first invention is characterized by containing by mass percent Al: 10.0 to 13.0%, Si: 0.3 to 1.5%, and Mn: 0.1 to 1.0%, the rest being Mg and unavoidable impurities.
The magnesium alloys of the second invention are characterized by containing by mass percent Al: 10.0 to 13.0%, Si: 0.3 to 1.5%, Mn: 0.1 to 1.0%, and Zn: less than 0.8%, the rest being Mg and unavoidable impurities.
The magnesium alloys of the third invention are characterized by further containing by mass percent 10 ppm to 0.1% in total amount one kind or two kinds or more of Be, Ca, Sr, Ba and Mm (mesh metal) in the magnesium alloys as set forth in the first or second inventions.
The materials of magnesium alloys of the fourth invention are characterized in that the instant materials are produced by an injection molding process of injecting alloys as set forth in any of the first to third inventions under the semi solid condition being 50% or less in solid phase rate into the die.